Air pollution linked to cognitive decline in later years

NEW YORK (Reuters Health) - The tiny particles in vehicle
exhaust and other sources of air pollution may hasten cognitive
decline in older adults, according to a new U. S. study.

"We decided to examine the link between air pollution and
cognitive function in older adults because there is growing
evidence that fine particulate matter air pollution affects
brain health and development, but relatively little attention
has been given to what this means for the aging brain," said
Jennifer Ailshire, who co-wrote the report.

Ailshire is with the Center for Biodemography and Population
Health and the Andrus Gerontology Center at the University of
Southern California in Los Angeles.

She, along with Philippa Clarke of the Institute for Social
Research at the University of Michigan, Ann Arbor, say that
based on their results, improvements in air quality may be an
important strategy for reducing age-related cognitive decline.

There has been some evidence that people living in more
polluted areas have greater rates of cognitive decline, and the
link is not explained by wealth or other social factors, the
researchers point out in The Journals of Gerontology: Series B.

They gathered information from one wave of a large ongoing
survey started in 1986, and focused their analysis on 780
participants who were 55 years of age or older at the time of
the 2001/2002 survey.

Routine measurement of air pollution by census tract did not
start until the late 1990s, they explain.

Cognitive function was measured by math and memory tests and
participants got a score based on the number of cognitive errors
they made.

Air pollution levels for each participant's neighborhood
were calculated using fine particulate levels reported by the
U.S. EPA's Air Quality System. Those pollution particles 2.5
microns or smaller (PM2.5) can travel deep into the lungs and
enter the bloodstream, past research has shown.

Ailshire and Clarke found the average PM2.5 concentrations
in the study participants' environments were 13.8 micrograms per
cubic meter, which is above the EPA's air quality standard of 12
micrograms per cubic meter.

Then they compared the cognitive error scores to pollution
levels and found that people living in high pollution areas,
with 15 micrograms per cubic meter or more of PM2.5 had error
scores one and a half times those of the participants who lived
in low pollution areas with no more than 5 micrograms per cubic
meter.

Poverty and other social factors as well as health problems
can influence cognitive function, the authors note. And poorer
neighborhoods tend to be more polluted. But after the
researchers adjusted for education, employment, gender, marital
status and several other factors, the differences in cognitive
error rates remained.

"The emerging evidence showing a link between air pollution
and cognitive function suggests air pollution may harm the brain
as well as the heart and lungs," Ailshire said in an email.

"Ideally," she and Clarke wrote, they would want long-term
data and more exact individual pollution exposures to assess the
importance of PM2.5 in cognitive function.

Jennifer Weuve said the new research joins a growing number
of large studies that suggest "higher exposures to everyday air
pollution affect aging brains' ability to think."

Weuve, who was not involved in the study, is a researcher at
the Rush Institute for Healthy Aging at Rush University Medical
Center in Chicago.

Scientists "believe that particulate matter may affect
cognitive function in older adults by its harmful effects on the
cardiovascular system - which is connected to the brain through
blood vessels - and possibly by directly acting on the brain
itself," Weuve said.

This type of air pollution is difficult to avoid. The most
important action is the one we take as a society, by regulating
the amount of pollution that gets emitted into our air, not by
individual actions, she said.

"Short of confining oneself to an indoor space with filtered
air, it is extraordinarily difficult (and absurd) to imagine any
one person being able to, for example, stop the air pollution
that emanates into his or her environment from an industrial
plant tens or hundreds of miles away," Weuve said.

"Although finding a link between the air we breathe on a
daily basis and our long-term brain health is alarming, the good
news is that we have made remarkable progress in the last decade
in reducing levels of air pollution across the country, and
there are efforts underway to further reduce air pollution,"
Ailshire said.

Still, she added, the public should understand that there
are health risks to living in polluted environments,
particularly for older adults, and we should all be more aware
of issues related to air quality.

SOURCE: http://bit.ly/1y8PRSx The Journals of Gerontology:
Series B, online June 6, 2014.